Technical Abstract:
Eutypa lata ascospores strictly contribute to the spread of Eutypa dieback of grapevine. Conidia of the fungus are produced in nature, but are not infectious. Ascospores are released from perithecia following rain and are wind-dispersed. They infect grapevine vascular tissue by colonizing susceptible wounds (pruning wounds, freeze-damaged tissue). Past research on the spread of Eutypa dieback supports both local and distant origins of ascospore inoculum in individual vineyards. However, the epidemiology of this disease was mainly studied in Mediterranean regions. The timing of spore production and infection is not known in cold climates, where freezing winter temperatures may restrict dormant season spore dispersal, temporally and spatially. Our objective was to examine the diversity of E. lata populations from North American vineyards in regions representing both Mediterranean and cold climates. To determine the frequency of gene flow within and between vineyards, we isolated and characterized nine E. lata-specific microsatellite markers. Eutypa lata was collected from diseased vineyards located in California, Connecticut, New York and Rhode Island. Cultures were initially identified based on culture morphology and DNA sequencing of the rDNA internal transcribed spacer region (ITS). Despite similar culture morphology and minimal sequence differences among a total of 95 isolates, not all microsatellite markers amplified DNA from all isolates. Our findings of unique alleles among East and West coast populations of E. lata, in addition to a low frequency of gene flow suggest that East and West coast populations are somewhat isolated from each other.